Roll holder device

ABSTRACT

A roll holder device is composed of a first holder and a second holder. The first holder is provided with a rotary-claw unit for a forward rotation, which works when the first holder rotates in a forward direction (clockwise direction). The rotary-claw unit includes a rotary claw, a retainer, a compression spring, a stopper and so forth. The rotary claw is rotatable around a shaft attached to the retainer. The compression spring biases the retainer toward the stopper in the clockwise direction. In attaching the first holder to a recording-paper roll, the rotary claw abuts on and rotates along an inner circumference of a core of the recording-paper roll.

FIELD OF THE INVENTION

The present invention relates to a roll holder device comprising a pair of holders attached to both ends of a sheet roll, in which a strip of a sheet is wound around a core, and rotating together with the sheet roll.

BACKGROUND OF THE INVENTION

A photographic printer and a color thermal printer employ a recording-paper roll in which a strip of a recording paper is wound around a cylindrical core. The recording paper is drawn out of the recording-paper roll and an image is recorded thereon. After that, the recording paper is cut in a prescribed size.

At a time when the recording-paper roll is set to a paper feeder of the printer, the recording-paper roll is mounted on a roll holder device so as to be rotatably supported. The roll holder device comprises a pair of holders attached to both ends of the recording-paper roll. The holder has a fit portion fitting to an inner circumference of the core, and a rod supported by support members disposed in the paper feeder.

The recording-paper roll is integrally rotated with the pair of the holders. In a known manner for rotating the recording-paper roll, a drive gear is formed on one of the holders to rotate the recording-paper roll via this drive gear. In this manner, however, the holder slips relative to the core if the holder is loosely engaged with the core. In consideration of this, techniques for preventing the holder from slipping are proposed.

As to the technique for preventing the holder from slipping, it is known that a key is formed on the holder and a key groove engaging with the key is formed on the core. In this technique, however, it is required to form the key and the key groove with great accuracy. Although this technique is advantageous in a case using a plastic core, it is difficult to adopt this technique in a case using a paper core, since the manufacturing cost remarkably increases.

As to the technique for preventing the holder from slipping on the paper core, it is known to utilize a claw member, which is formed at the fit portion of the holder, and a spring for biasing the claw member in a radial direction toward the outside (see Japanese Patent Laid-Open Publication No. 2003-246508, for instance). The top of the claw member is a pointed claw biting into the inner circumference of the core.

In the technique utilizing the claw member and the spring, when the biasing force of the spring is strong, the claw member strongly bites so that slipping is surely prevented. However, there arises a problem in that friction increases at a time when the holder is attached to the core. Consequently, operability of the holder deteriorates. In particular, when a user hurriedly performs the attachment operation of the holder, sometimes the holder is incompletely attached to the recording-paper roll. If the holder incompletely attached to the recording-paper roll is set to the paper feeder, a width of the recording paper is not sufficiently regulated. Thus, there arise problems in that the recording paper skews at the rotational drive time and printing is not performed within a proper area. Meanwhile, when the biasing force of the spring is weak, the friction of the attachment time is small so that the holder is easily attached to the core. However, there arises a problem in that the holder slips, since the claw member does not strongly bite. Further, when the user attaches the holder to the core, a hand of the user is likely to be damaged by contacting with the claw member.

SUMMARY OF THE INVENTION

In view of the foregoing, it is a primary object of the present invention to provide a roll holder device in which a holder is surely prevented from slipping relative to a sheet roll after attachment of the holder.

It is a second object of the present invention to provide a roll holder device having excellent operability and high safeness.

It is a third object of the present invention to provide a roll holder device in which a holder is adapted to be surely attached to a sheet roll.

In order to achieve the above and other objects, the roll holder device according to the present invention comprises a first holder and a second holder, which are attached to both ends of a sheet roll formed by winding a strip of a sheet around a cylindrical paper core. The holders hold the sheet roll and integrally rotate therewith. At least one of the first and second holders is provided with a fit portion for fitting to an inner circumference of the core. The roll holder device further comprises at least one rotary member disposed at the fit portion, and a rotary-member biasing mechanism by which the rotary member is biased to protrude from the fit portion. The rotary member abuts on and rotates along the inner circumference of the core at an attachment time of the roll holder device. The rotary-member biasing mechanism presses the rotary member against the inner circumference of the core at the attachment time.

In a preferred embodiment, the rotary-member biasing mechanism includes a rotary-member support shaft for rotatably supporting the rotary member, a retainer for retaining the rotary member via the rotary-member support shaft, a retainer support shaft for rotatably supporting the retainer, and a bias member for biasing the retainer so as to pivot the retainer around the retainer support shaft. The rotary-member support shaft is attached to the retainer so as to extend in a direction perpendicular to an attachment direction of the roll holder device. The retainer support shaft is attached to the fit portion so as to extend in parallel to the attachment direction.

It is preferable that the rotary member is a disk and is movable between a first projection position and a second projection position. In the first projection position, the rotary member most protrudes from the fit portion. In the second projection position, the rotary member is pushed back against the rotary-member biasing mechanism in association with the attachment operation to press the inner circumference of the core. When the rotary member is kept in the second projection position, it is preferable that the rotary member tilts relative to a normal line passing a contact point of the inner circumference of the core. In virtue of this, when the roll holder device rotates, the rotary member is strongly pressed against the inner circumference of the core so that the roll holder device is surely prevented from slipping.

It is preferable to provide first and second types of the rotary members. The rotary member of the first type presses the inner circumference of the core in a condition that the rotary member tilts in an anterior direction of a time when the first and second holders rotate in a forward direction. The rotary member of the second type presses the inner circumference of the core in a condition that the rotary member tilts in an anterior direction of a time when the first and second holders rotate in a backward direction.

It is preferable to dispose the rotary members and the rotary-member biasing mechanisms at predetermined intervals in a circumferential direction of the fit portion. In this case, uniform force is applied to the core when the roll holder device rotates. Thus, the sheet roll is prevented from being biased during rotation.

According to the present invention, the rotary member abuts on and rotates along the inner circumference of the core at the attachment time of the roll holder device so that attachment resistance is reduced. Consequently, the attachment operation is easily performed. In addition, the rotary member is strongly pressed against the inner circumference of the core after the attachment so that the holder is surely prevented from slipping.

The roll holder device further comprises a holder interlocking mechanism for connecting the first and second holders by an attractive force. The holder interlocking mechanism generates the attractive force when the first and second holders approach each other within a predetermined length. At the attachment time of the holder, attachment resistance is caused by pressing the rotary member against the inner circumference of the core. When F1 represents the attachment resistance and F2 represents the attractive force generated by the holder interlocking mechanism, a condition of F1<F2 is satisfied.

The first and second holders have a rod, which projects to the outside of the interlocked holders. The rod is settable to a pair of support members. When LA represents an interval of the completely interlocked first and second holders, LB represents an interval of the support members, and LC represents the predetermined length of the first and second holders wherein the attractive force is generated, a condition of LA<LB<LC is satisfied.

The holder interlocking mechanism includes a first engagement member, a projection, a biasing member and a second engagement member. The first engagement member is disposed in one of the first and second holders and is formed in a triangle shape. The first engagement member further has first and second incline surfaces located at both sides of its central top portion. The projection is disposed in the other of the first and second holders so as to extend in a radial direction. The first engagement member abuts on the projection at the attachment time. The biasing member biases the first engagement member in the radial direction, and in this state, the first and second incline surfaces slide on the projection at the attachment time. When the second incline surface slides on the projection, the attractive force is generated. After the second incline surface has slid on the projection, the first engagement member engages with the second engagement member.

According to the present invention, it is possible to surely attach the first and second holders to the sheet roll. Thus, the sheet roll is accurately regulated in a width direction. The first and second holders are prevented from being set in an incomplete attachment state. A user can perform the setting operation without carefully confirming whether the first and second holders are completely attached or not at the attachment time. In virtue of this, the setting operation is simplified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a paper tray and a roll holder device attached to a recording-paper roll;

FIG. 2 is an exploded perspective view of the recording-paper roll and the roll holder device;

FIG. 3 is a section view of the roll holder device taken in an axial direction;

FIG. 4 is a section view of the roll holder device taken in a radial direction;

FIG. 5 is an explanatory illustration showing an angle, which is formed by a radial direction of a rotary claw and a normal-line direction regarding a contact point of an inner circumference of a core, under the condition that the rotary claw is kept in a press position;

FIG. 6 is an explanatory illustration showing an attractive force generated by an interlocking mechanism;

FIG. 7 is an explanatory illustration showing an interval of holders in a state that the holders attract each other;

FIGS. 8A and 8B are explanatory illustrations explaining an attachment operation of the roll holder device;

FIG. 9 is an explanatory illustration showing the rotary claw biting an inner circumference of a core; and

FIGS. 10A and 10B are explanatory illustrations explaining the attachment operation of the roll holder device in a case that the first holder is incompletely attached.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, a recording-paper roll 3 in which a strip of a recording paper 2 is wound in a roll form is used in a state that a roll holder device 4 is attached to both ends thereof. A paper tray 5 is fitted into a printer body, which is not shown, so as to be pulled out. The paper tray 5 is pulled out to set the recording-paper roll 3 to which the roll holder device 4 is attached. After that, the paper tray 5 is pushed into the printer body to load the recording-paper roll 3 therein.

The paper tray 5 is provided with two support plates 10 and 11 having support concaves 10 a and 10 b formed in a U-like shape. A rod 12 of the roll holder device 4 is supported by the concaves 10 a and 11 a. Two guide rails 13 and 14 are fixed to the paper tray 5. The guide rails 13 and 14 are respectively provided with ridges 13 a and 14 a formed in a longitudinal direction. The ridges 13 a and 14 a are guided when the paper tray 5 is moved.

The guide rails 13 and 14 are provided with lock pins 15 and 16, which are locked by a lock mechanism not shown when the paper tray 5 is contained in the printer body. The paper tray 5 is provided with a flap 18 being rotatable around a shaft 17. The flap 18 is urged by a spring in a circumferential direction of the shaft 17, and is rotated by a hand inserted into an under portion of the flap 18. By swinging the flap 18 against the spring, it is possible to release the lock of the lock mechanism. Incidentally, the lock is adapted not to be released during transportation of the recording paper 2, even if the flap 18 is handled. Thus, it is prevented that the paper tray 5 is mistakenly pulled out during the transportation of the recording paper 2. Thus, a harmful influence is not exerted on operations for transporting the recording paper and for recording an image.

As shown in FIG. 2, the recording-paper roll 3 is formed by winding the strip of the recording paper 2 around a cylindrical paper core 20. The roll holder device 4 comprises a first holder 21 and a second holder 22. The first holder 21 is attached to one end of the recording-paper roll 3 and the second holder 22 is attached to the other end thereof.

As shown in FIGS. 2 and 3, the first holder 21 comprises a flange 30, a circular protrusion 33 (see FIG. 1) disposed at the outside of the flange 30, and a bearing 34 (see FIG. 1) rotatably supported by the rod 12. The first holder 21 is provided with a fit portion 31 disposed at the inside of the flange 30. The interior of the fit portion 31 is provided with two rotary-claw units 28 for forward rotation and two rotary-claw units 29 for backward rotation. These rotary-claw units prevent the first holder 21 from slipping relative to the recording-paper roll 3.

The flange 30 is a thin plate substantially having a regular dodecagon shape. The flange 30 confronts one end of the recording-paper roll 3 to regulate movement thereof in a width direction. The fit portion 31 is formed in a cylindrical shape, and an outer diameter thereof is substantially identical with an inner diameter of the core 20. The fit portion 31 is provided with a step 35 to engage with a step 76, which is described later, in association with an attachment operation. The fit portion 31 is further provided with engagement holes 36 to engage with engagement pieces 77, which are described later, in association with the attachment operation. The engagement holes 36 are formed by four so as to have predetermined intervals in a circumferential direction of the fit portion 31. Furthermore, the fit portion 31 is provided with a projection 31 b projecting toward the inside thereof.

A gear 37 (see FIG. 1) is formed on the periphery of the circular protrusion 33. The gear 37 meshes with an actuator of the printer body, which is not shown, when the paper tray 5 (see FIG. 1) is inserted into the printer body. By means of the actuator, the roll holder device 4 is rotated in forward and backward directions. When the roll holder device 4 is rotated in the forward direction, the recording paper 2 is drawn out of the recording-paper roll 3. When the roll holder device 4 is rotated in the backward direction, the recording paper 2 is rewound to the recording-paper roll 3.

The second holder 22 comprises a flange 70, a fit portion 71 disposed at the inside of the flange 70, an interlocking mechanism 72 for connecting the holders, two circular protrusions 73 and 74 disposed at the outside of the flange 70, and a bearing 75 rotatably supported by the rod 12.

The flange 70 is a thin plate substantially having a regular dodecagon shape, similarly to the flange 30. The flange 70 confronts the other end of the recording-paper roll 3. The fit portion 71 is formed in a cylindrical shape, and an outer diameter thereof is identical with that of the fit portion 31. The fit portion 71 is provided with the step 76.

As shown in FIG. 4, the rotary-claw unit 28 for the forward rotation comprises a rotary claw 38 and a biasing mechanism 45 for biasing the rotary claw 38. The rotary-claw unit 28 works when the respective holders 21 and 22 rotate in the forward direction (clockwise direction). The biasing mechanism 45 includes a shaft 39, a retainer 40, a support shaft 41, a compression spring 42 and a stopper 44. The two rotary-claw units 28 are disposed at symmetry positions about the rod 12. Incidentally, the rotary-claw units for the forward rotation may be provided by three or more. In this case, it is preferable to dispose the rotary-claw units at constant intervals in a circumferential direction of the fit portion 31.

The rotary claw 38 has a disk shape and is provided with an edge portion 38 a formed by cutting a part of an anterior side of a time when the first holder 21 rotates in the forward direction. The edge portion 38 a bites into an inner circumference 20 a (see FIG. 2) of the core 20. The rotary claw 38 is rotatable around the shaft 39 attached to the retainer 40, which is rotatable around the support shaft 41 attached to the fit portion 31. The shaft 39 is perpendicular to the support shaft 41 extending in parallel to the rod 12.

The compression spring 42 biases the retainer 40 in the clockwise direction around the support shaft 41. A moving range of the retainer 40 in the biasing direction is regulated by the stopper 44. The rotary claw 38 moves between a projection position where a part thereof projects from an opening 43 formed in the fit portion 31, and a press position where the rotary claw 38 is pressed against the inner circumference 20 a of the core 20 as shown in FIG. 5. The rotary claw 38 is pushed toward the inside of the fit portion 31 in association with the attachment operation of the roll holder device 4.

When the rotary claw 38 is kept in the press position, the rotary claw 38 tilts relative to a normal line 47 passing a contact point of the inner circumference 20 a of the core 20. An angle formed by the rotary claw 38 and the normal line 47 is represented by θA. In FIG. 5, a radial direction of the rotary claw 38 is represented by a line 46. In particular, the rotary claw 38 for the forward rotation is adapted to tilt in an advancing direction when the first holder 21 rotates in the forward direction (clockwise direction). In other words, the line 46 is adapted to be located at an anterior side of the normal line 47 in the advancing direction. In virtue of this, the rotary claw 38 is strongly pressed against the inner circumference 20 a of the core 20 when the first holder 21 is rotated in the forward direction.

The two rotary-claw units 29 for the backward rotation are disposed at symmetry positions about the rod 12, and work when the respective holders 21 and 22 are rotated in the backward direction (counterclockwise direction). The rotary-claw unit 29 is composed of a rotary claw 48 and a biasing mechanism 55 for biasing the rotary claw 48.

A structure of the rotary claw 48 is similar to that of the rotary claw 38. In this regard, an edge portion 48 a formed on the rotary claw 48 is different in a point that the cut part thereof is located at an anterior side of a time when the first holder 21 is rotated in the backward direction.

A structure of the biasing mechanism 55 is similar to that of the biasing mechanism 45. The biasing mechanism 55 includes a shaft 49, a retainer 50, a support shaft 51, a compression spring 52, and a stopper 54. In this regard, the retainer 50 is different in a point that the compression spring 52 biases the retainer 50 in the counterclockwise direction around the support shaft 51. The rotary claw 48 moves between a projection position where a part thereof projects from an opening 53 formed in the fit portion 31, and a press position where the rotary claw 48 is pressed against the inner circumference 20 a of the core 20. The rotary claw 48 is pushed toward the inside of the fit portion 31 in association with the attachment operation of the roll holder device 4.

When the rotary claw 48 is kept in the press position, the rotary claw 48 tilts relative to a normal line 57 passing a contact point of the inner circumference 20 a of the core 20. An angle formed by the rotary claw 48 and the normal line 57 is represented by θB. In FIG. 5, a radial direction of the rotary claw 48 is represented by a line 56. The rotary claw 48 is strongly pressed against the inner circumference 20 a of the core 20 when the first holder 21 is rotated in the backward direction.

Although the attachment operation for inserting the first holder 21 into the recording-paper roll 3 is described later, resistance occurs during the attachment operation of the first holder 21. This resistance is defined as attachment resistance represented by F1. The attachment resistance F1 is adapted to be reduced in comparison with that of a conventional device.

As shown in FIG. 6, the interlocking mechanism 72 includes the engagement piece 77 and a compression spring 78 for urging the engagement piece 77 toward the outside in a radial direction. The engagement piece 77 is disposed inside a guide hole 79 formed in the fit portion 71. The engagement piece 77 has a mountain-like shape including a first incline surface 77 a and a second incline surface 77 b. The second holder 22 is pushed against the first holder 21 until a certain position, and the second incline surface 77 b of the engagement piece 77 abuts on the projection 31 b. At this time, the engagement piece 77 receives a force from the projection 31 b. By virtue of an axial component of the force received by the engagement piece 77, the holders attract each other. This force is defined as attractive force represented by F2. Compared with the attachment resistance F1, a relation of F1<F2 is maintained.

In a condition that the holders are completely joined, a holder interval is represented by LA (see FIG. 3). The holder interval is a distance extending from an end of the circular protrusion 33 of the first holder 21 to an end of the circular protrusions 73 and 74 of the second holder 22. Moreover, a distance between the support plates 10 and 11 of the paper tray 5 is represented by LB (see FIG. 1). As shown in FIG. 7, when the second holder 22 is pushed and the holders attract each other, the holder interval is represented by LC. In this regard, the interval LC is equal to LA plus LD, wherein LD represents a length of the incline surface 77 b orthogonally projected toward the rod 12. The device of this embodiment is adapted to satisfy a relation of LA<LB<LC.

An operation of the above structure is described below. The paper tray 5 is drawn out of the printer body and the used recording-paper roll is removed. Thus, it becomes possible to place the unused recording-paper roll 3.

In attaching the roll holder device 4 to the recording-paper roll 3, the first holder 21 and the second holder 22 may be attached in this order or in a reverse order thereof. In this embodiment, the former order is adopted.

First of all, as shown in FIG. 8A, the first holder 21 is squeezed in the condition that the fit portion 31 of the first holder 21 fits to the inner circumference of the core 20 of the recording-paper roll 3. When the first holder 21 is squeezed, an outer circumference 31 a of the fit portion 31 slides on the inner circumference 20 a of the core 20. In the meantime, such as shown in FIG. 9, the rotary claws 38 and 48 of the rotary-claw units 28 and 29 abut on the inner circumference 20 a and are pressed against this circumference 20 a by the biasing force of the respective compression springs 42 and 52. The rotary claws 38 and 48 are moved from the projection position to the press position.

As the first holder 21 is further squeezed, the rotary claws 38 and 48 move along the inner circumference 20 a while rotating around the shafts 39 and 49. By squeezing the first holder 21 until a place where the inside surface of the flange 30 abuts on the end of the recording-paper roll, the attachment of the first holder 21 is completed. The edge portions 38 a and 48 a of the rotary claws 38 and 48 slightly enter the inner circumference 20 a.

As described above, the rotary claws 38 and 48 abut on the inner circumference 20 a of the core 20 and rotate at the attachment time so that the attachment resistance F1 is reduced. Thus, the attachment is easily performed. In addition, the rotary claws 38 and 48 strongly press the inner circumference 20 a of the core 20 after the attachment.

Successively, as shown in FIG. 8B, the second holder 22 is squeezed in the condition that the fit portion 71 of the second holder 22 fits to the inner circumference 20 a of the core 20. An outer circumference 71 a of the fit portion 71 slides on the inner circumference 20 a of the core 20, and then, the incline surface 77 a of the engagement piece 77 abuts on the projection 31 b. As the second holder 22 is further squeezed, the top of the engagement piece 77 gets over the projection 31 b and the incline surface 77 b abuts on the projection 31 b. The attractive force F2 is automatically caused between the first and second holders 21 and 22. The attractive force F2 applied to the second holder 22 is shown in FIG. 8B. Since the holders attract each other, the engagement piece 77 enters the engagement hole 36 and engages therewith to interlock the holders. The interval of the holders becomes LA. In this way, the attachment of the roll holder device 4 is completed.

In the above, the first holder 21 is surely attached to the recording-paper roll 3 before attaching the second holder 22. However, when the user hurriedly performs the operation, sometimes the first holder 21 is incompletely attached. Even in such a case, the roll holder device 4 of the present invention can be surely attached. Referring to FIG. 10, is described an attachment operation performed in the case that the first holder 21 is incompletely attached.

As shown in FIG. 10A, the first holder 21 is not squeezed until the position where the inner surface of the flange 30 abuts on the end of the recording-paper roll 3. In this condition, the second holder 22 is squeezed and the inner surface of the flange 70 abuts on the other end of the recording-paper roll 3 such as shown in FIG. 10B. As the second holder 22 is further squeezed, the top of the engagement piece 77 gets over the projection 31 b, and then, the incline surface 77 b abuts on the projection 31 b. The attractive force F2 is automatically caused between the first and second holders 21 and 22. Since the attractive force F2 is greater than the attachment resistance F1, the holders attracts each other without regard to the attachment resistance F1. By the way, in FIG. 10B, the attractive force F2 and the attachment resistance F1 applied to the second holder 22 and the recording-paper roll 3 are shown. The holders are completely interlocked and the interval thereof becomes LA. In this way, the attachment of the roll holder device 4 is completed in the case that the first holder 21 is incompletely attached before attaching the second holder 22.

The recoding-paper roll 3 to which the roll holder device 4 is attached is set to the paper tray 5 in a state that both ends of the rod 12 are supported by the support plates 10 and 11. At this time, in order to set the first and second holders 21 and 22 to the support plates 10 and 11, it is necessary to make the holder interval shorter than LC by hand. In making the holder interval shorter than LC, the holders automatically attract each other and the holder interval becomes LA. The first and second holders 21 and 22 are surely attached. Thus, the first and second holders 21 and 22 are prevented from being set in an incomplete attachment state. The user can perform the setting operation without carefully confirming whether the first and second holders 21 and 22 are completely attached or not at the attachment time. In virtue of this, the setting operation is simplified.

After setting the recording-paper roll 3, the paper tray 5 is pushed into the printer body to lard the recording-paper roll 3 in the printer body. Upon pushing the paper tray 5 into the printer body, the gear 37 meshes with the actuator disposed in the printer body. By means of the actuator, the gear 37 is driven so that the first and second holders 21 and 22 are rotated in the forward and backward directions.

In response to an instruction for advancing the recording paper 2, the first and second holders 21 and 22 are rotated in the forward direction (clockwise direction in FIG. 9). At this time, the edge portion 38 a of the rotary claw 38 deeply bites into the inner circumference 20 a of the core 20 so that the recording-paper roll 3 surely rotates together with the roll holder device 4 without slipping. As the recording-paper roll 3 rotates, the recording paper 2 is advanced. On the advanced recording paper 2, an image is recorded. The recorded area is cut and discharged from the printer body.

After the image recording operation, an instruction for rewinding the recording paper 2 is outputted to rotate the first and second holders 21 and 22 in the backward direction (counterclockwise direction in FIG. 9). At this time, the edge portion 48 a of the rotary claw 48 deeply bites into the inner circumference 20 a of the core 20 so that the recording-paper roll 3 surely rotates together with the roll holder device 4 without slipping. As the recording-paper roll 3 rotates in the backward direction, the recording paper 2 is rewound.

When the recording paper 2 of the roll 3 is wholly used, the paper tray 5 is drawn out and the roll holder device 4 is detached from the used recording-paper roll. In applying a force to separate the second holder 22 from the core 20 a and the first holder 21, the engagement piece 77 exits from the engagement hole 36. Then, it becomes possible to detach the second holder 22. After detaching the second holder 22, a force is applied to separate the first holder 21 from the core 20. Upon this, the rotary claws 38 and 48 rotate along the inner circumference 20 a of the core 20 and the first holder 21 is detached. After that, the roll holder device 4 is attached to the unused recording-paper roll. The above-described operations are repeated.

In the above embodiment, the recording paper is used as a sheet. However, the sheet may be a paper to be used for another purpose excepting the image recording. Moreover, the sheet may be made of a material excepting the paper.

In the above embodiment, the rotary claws for the forward and backward rotations are provided. However, either of the rotary claws for the forward and backward rotations may be merely provided. In the above embodiment, the rotary claws of the same sort are provided by two. However, the sole rotary claw may be provided, and the rotary claws may be provided by three or more.

In the above embodiment, the holders are interlocked in association with the attachment. However, the respective holders may be provided with the rotary claws without interlocking the holders.

Although the present invention has been fully described by way of the preferred embodiments thereof with reference to the accompanying drawings, various changes and modifications will be apparent to those having skill in this field. Therefore, unless otherwise these changes and modifications depart from the scope of the present invention, they should be construed as included therein. 

1. A roll holder device for a sheet roll in which a strip of a sheet is wound around a cylindrical core, said roll holder device comprising: a first holder attached to one end of said sheet roll; a second holder attached to the other end of said sheet roll, said first and second holders holding said sheet roll and integrally rotating therewith; a fit portion equipped on at least one of said first and second holders, said fit portion being squeezed into said core and fitting to an inner circumference thereof; at least one rotary member disposed at said fit portion, said rotary member abutting on said inner circumference of said core and rotating in attaching said fit portion to said core; and a rotary-member biasing mechanism for projecting said rotary member from said fit portion and for biasing said rotary member so as to press the inner circumference of said core.
 2. The roll holder device according to claim 1, wherein said core is made of a paper.
 3. The roll holder device according to claim 2, wherein each of said first and second holders has said fit portion, and ends of the respective fit portions are connected.
 4. The roll holder device according to claim 2, wherein said rotary-member biasing mechanism includes: a rotary-member support shaft for rotatably supporting said rotary member, said rotary-member support shaft extending in a direction perpendicular to an attachment direction of said fit portion; a retainer for retaining said rotary member via said rotary-member support shaft; a retainer support shaft attached to said fit portion to rotatably support said retainer, said retainer support shaft extending in parallel to said attachment direction; and a biasing member for biasing said retainer so as to pivot said retainer around said retainer support shaft.
 5. The roll holder device according to claim 4, wherein said rotary-member biasing mechanism further includes: a stopper for regulating a pivot of said retainer biased by said biasing member.
 6. The roll holder device according to claim 5, wherein said biasing member is a compression spring.
 7. The roll holder device according to claim 2, wherein said rotary member is a disk.
 8. The roll holder device according to claim 7, wherein a part of said rotary member projects toward said core via an opening formed in a circumference of said fit portion.
 9. The roll holder device according to claim 8, wherein said rotary member is movable between a first projection position where said rotary member most projects from said fit portion, and a second projection position where said rotary member is pushed back against said rotary-member biasing mechanism in association with an attachment operation of said fit portion to press said inner circumference of said core.
 10. The roll holder device according to claim 9, wherein when said rotary member is kept in said second projection position, said rotary member tilts relative to a normal line passing a contact point of said inner circumference of said core.
 11. The roll holder device according to claim 10, wherein there are first and second types of said rotary members, said rotary member of the first type pressing said inner circumference of said core in a condition that the rotary member tilts in an anterior direction of a time when said first and second holders rotate in a forward direction, and said rotary member of the second type pressing said inner circumference of said core in a condition that the rotary member tilts in an anterior direction of a time when said first and second holders rotate in a backward direction.
 12. The roll holder device according to claim 2, wherein said rotary member and said rotary-member biasing mechanism compose a unit, and a plurality of said units are disposed at regular intervals in a circumferential direction of said fit portion.
 13. The roll holder device according to claim 1, further comprising: a holder interlocking mechanism for connecting said first and second holders, said holder interlocking mechanism generating an attractive force, by which said holders attract each other, when an interval of said holders is predetermined length or less in attaching said first and second holders to said sheet roll, wherein a condition of F1<F2 is satisfied when F1 represents attachment resistance caused by pressing said rotary member against said inner circumference of said core and F2 represents said attractive force generated by said holder interlocking mechanism.
 14. The roll holder device according to claim 13, wherein said first holder has a rod passing therethrough, and said rod projects to the outside of said second holder through a bearing of said second holder when said first and second holders are attached to said sheet roll.
 15. The roll holder device according to claim 14, wherein both ends of said rod projecting from said first holder and said second holder are settable to a pair of support members and the following condition is satisfied: LA<LB<LCwherein LA represents an interval of the completely interlocked first and second holders, LB represents an interval of said support members, and LC represents said predetermined length of said first and second holders.
 16. The roll holder device according to claim 13, wherein said rotary-member biasing mechanism includes: a rotary-member support shaft for rotatably supporting said rotary member, said rotary-member support shaft extending in a direction perpendicular to an attachment direction of said fit portion; a retainer for retaining said rotary member via said rotary-member support shaft; a retainer support shaft attached to said fit portion to rotatably support said retainer, said retainer support shaft extending in parallel to said attachment direction; and a biasing member for biasing said retainer so as to pivot said retainer around said retainer support shaft.
 17. The roll holder device according to claim 16, wherein said biasing member is a compression spring.
 18. The roll holder device according to claim 13, wherein said holder interlocking mechanism includes: a first engagement member disposed in one of said first and second holders, said first engagement member being formed in a triangle shape having first and second incline surfaces located at both sides of its central top portion; a projection disposed in the other of said first and second holders to project in a radial direction of the holder, said projection coming into contact with said first engagement member in connecting said holders; a biasing member for biasing said first engagement member in said radial direction to sequentially slide said first and second incline surfaces on said projection in connecting said holders, said biasing member generating said attractive force when sliding said second incline surface on said projection; and a second engagement member for engaging with said first engagement member after sliding said second incline surface on said projection.
 19. The roll holder device according to claim 18, wherein said fit portion is equipped on said first holder, said first engagement member and said biasing member are disposed in said second holder, and said projection and said second engagement member are disposed in said fit portion.
 20. The roll holder device according to claim 19, wherein said biasing member is a compression spring, and said second engagement member is a hole formed in a circumference of said fit portion. 